Periodically operating controlling device



Aug. 3, 1954 K. F. TROMP PERIODICALLY OPERATING CONTROLLING DEVICE FildJune 27, 1950 4 Sheets-Sheet 1 Aug. 3, 1954 K, TRQMP 2,685,295

PERIODICALLY OPERATING CONTROLLING DEVICE Filed June 27, 1950 4Sheets-Sheet 2 1954 K. F. TROMP PERIODICALLY OPERATING CONTROLLINGDEVICE Filed June 27, 1950 4 Sheets-Sheet 3 4 zzvnsvvrole jam: F Warn 3,1954 K. F. TROMP 2,685,295

PERIODICALLY OPERATING CONTROLLING msvxcz Filed June 27, 1950 4Sheets-Sheet 4 ZZ/l/EN re a Ween was Patented Aug. 3, 1954 PERIODICALLYOPERATING CONTROLLING DEVICE Klaas F. Tromp, Kerkrade, NetherlandsApplication June 27, 1950, Serial No. 170,521

Claims priority, application Great Britain March 14, 1950 9 Claims. 1

It is well-known in the art that any automatic controlling devicecomprises, in addition to means for measuring the magnitude to becontrolled, means for feeling or scanning the result of the measuringoperation and adjusting means adapted to be actuated by the feelerwhenever the actual value of the magnitude to be controlled differs fromthe proper value.

The limits between which the device will be capable of keeping theactual value of said magnitude will be narrowest if the influence of thefeeler on the result of the measuring means is a minimum and theadjustments effected by differences between the proper and the actualvalues of the magnitude to be controlled are not so considerable as togive rise to oscillation, i. e. a series of alternating positive andnegative differences between the two aforesaid values. Moreover, it isessential for the adjusting means to be capable of rapid adjustment.

My present invention provides a device that fully meets the saidrequirements. It consists herein that the feeler is caused to operateperiodically and that differences between the actual and the propervalues of the magnitude cause the adjusting means to be operated betweenthe limits of a relatively small range.

It is pertinent here to remark that the term proper value of themagnitude to be controlled does not imply one definite value only, butalso a restricted range of values.

In order that my invention may be fully understood by those skilled inthe art, I shall now proceed to describe it in further detail withreference to the appended drawing, which diagrammatically illustrates,in Fig. 1, Figs. 2 and 2a, Fig. 3, and Figs. 4 and 4a, respectively,four embodiments of the invention.

In Fig. 1, the numeral I designates a weighing beam. Suspended from oneend of said beam is a body 2, and suspended from the other end thereofis a suitably recessed or profiled block 3 loaded by a weight 4. Duringswinging movement of the beam I said block 3 is movable, with a veryslight clearance, across a fixed abutment 5.

A conduit 6 serves to feed a reservoir I with relatively heavy liquid,which is to be mixed with relatively light liquid supplied by a conduitIi provided with a valve 8 for controlling the amount of liquid flowingthrough conduit 6 in such manner as to keep the specific gravity of themixture in reservoir I as nearly as possible to the proper value. Theconduit for discharging the mixture from reservoir I is indicated by 9.Through a valve 9 a controlled amount of the liquid mixture is fed intoa vat II] enclosing the aforesaid body 2, which is thus permanentlysubmerged in the mixture without engaging the wall of the vat. Thelatter is provided with a weir II, and, in the bottom, with a dischargepipe I2. The liquid discharged by the weir II and by the pipe I2 isreturned to the conduit 9.

The valve 9 should be set as to ensure a permanent overflow of theliquid in vat I0, so that the surface of the liquid is kept at aconstant level and the mass of weight I should be such as to hold theweighing beam I in zero position as long as the liquid in vat II) hasthe proper density.

The device further comprises a cam disk I3 rotatable about a horizontalaxis, driven by a motor not shown and adapted to cooperate with rollersIda, Itb pivoted to the substantially horizontal arms of bell cranks [5aand I5b, respectively, loosely mounted for independent oscillation abouta common pivot I6. Said bell cranks are loaded by springs I'Ia andI'll), respectively, which tend to urge the rollers I411, I412 intoengagement with cam disk I3. The substantially vertical arms of the bellcranks are provided with feelers, i. e. pointed projections I8a and I8b,respectively, adapted to cooperate with the face of block 3 in front ofsaid feelers.

As long as rollers Ida, I4b engage the high portion of the periphery ofcam I3, the feelers I 8a, I8b clear the recessed face of block 3, sothat the latter has freedom of vertical movement across abutment 5.However, if the rollers reach the low portion of the cam, springs Ila,IIb urge said feelers into contact with block 3, which is thereby urgedinto engagement with said abutment.

As will be seen from the drawing, the portion of block 3 that is locatedin the plane of bell crank I5a has a recess of uniform depth throughabout the lower half of the block, whereas the portion that is locatedin the plane of bell crank I5b is similarly recessed through about theupper half of the block, it being understood that a narrow centralportion of the block is unrecessed.

Fig. 1 shows the position of the various parts when the density of theliquid mixture in vat I0 exceeds the proper value. It will be seen thatthe weighing beam has swung through a small angular distance inclockwise direction and block 3 is suspended a small distance below zeroor neutral position. Consequently, the feeler I811 of bell crank I5aengages a projecting or non-recessed portion of block 3 and the feelerI8b of bell crank I5b engages the bottom of a recessed portion. That isto say, bell crank I5b has swung in clockwise direction through asomewhat larger angular distance than bell crank l5a and has therebyclosed an electric spring contact i912 with which it is adapted tocooperate, whereas contact Ilia, located in the path of bell crank Iila,is still open. Closure of contact I91) switches in an electric motor 20to actuate, through a slip coupling (not shown), valve 8 in a directionas to increase the amount of light liquid supplied to vat [0.

Should the density of the liquid mixture in vat Ill have been too low,block 3 would have assumed a position above neutral or zero level, andits nonrecessed or projecting lower portion would have arrested bellcrank I512, while its recessed lower portion would have allowed bellcrank I5a to swing through an angular distance sufiicient to closespring contact I 9a, causing motor 29 to actuate valve 8 in a directionopposite that referred to above so as to decrease the amount of liquidflowing to vat Hi.

If the weighing beam I is horizontal and the low portion of cam l3causes both bell cranks l8a, [8b to swing towards block 3 under the influence of springs Ila, I'Ib, said cranks are both arrested by thecentral, non-recessed portion of the block, so that neither contact I9a,iSb is closed.

If the shape and the rotary speed of cam l3 are properly selected and asuitable reduction gear is interposed between motor 20 and valve 8, theweighing beam will be capable freely and gradually to resume zeroposition whenever, owing to the density of the liquid mixture in vat Illbeing too high or too low, it will have deflected in the one or theother direction. It is to be noted that in one revolution of cam I3motor 2%) actuates valve 8 only during a comparatively very shortperiod, during which the setting of the valve is altered only by a verysmall amount.

The fact that valve 8 is actuated periodically offers the advantage thatthe measuring means need not transmit power to the adjusting means, sothat their normal operation is not impaired. Moreover, this periodicadjustment is better adapted than a continuous adjustment to reducedeviations from the proper value to a minimum. In this connection itshould be borne in mind that it always takes some time for an adjustmentof valve 8 to be effective in reducing or increasing the density of theliquid in vat II], for the mo ment wherein valve 3 is adjusted and, as aconsequence, the density in container 1 is varied, the liquid in vat itstill has the improper density and the latter is increased or reducedonly gradually. If, during this time, the deflection of beam i wereallowed continuously to actuate valve 8, then in the moment wherein thebeam would resume its neutral position, the increase or decrease of thedensity of the liquid mixture in vat it would still continue, and aftersome time this would cause valve 8 to be actuated in the oppositedirection and to give rise to a similar phenomenon, so that the actualvalue of the density of the liquid mixture in vat I0 would oscillateabout the proper value of said magnitude. This oscillation is obviatedif the feelers (I811, (812) operate periodically, provided, of course,that thefrequency and the duration of the cooperation. between thefeelers and the block 3 be responsive to the length of time required forthe correction of the position of beam 1.

Figs. 2 and 2a illustrate a second embodiment of the invention, Fig. 2showing the weighing apparatus in elevation and Fig. 2d part of saidapparatus, together with the means controlled thereby, in top plan view.Similar parts are designated by the same reference numerals as in Fig.l. Vat l0 and associate parts are not shown.

Whereas, in accordance with Fig. l, the pointer of the weighingapparatus is rigidly secured to the beam I, the pointer 2| illustratedin Fig. 2 is hinged to said beam by means of a pivot pin 22 in suchmanner as to be adapted for swinging movement in a vertical plane atright angles to plane passing through the axis of the beam. Secured tosaid pointer, on either side thereof, are two suitably spaced blocks 3aand 3b in vertically staggered relation. The cam disk I3 here isrotatable about a vertical axis and cooperates with the roller I l onthe short arm of the horizontal bell crank I5. Spring I'I tends to holdroller [4 in engagement with the periphery of cam I3 and to move thelong arm of the bell crank towards pointer 2|.

As long as roller HI travels on the high portion of cam I3, the long armof the bell crank clears the pointer but the low portion of the camallows spring I1 to urge said arm into engagement with the pointer andto cause the same to swing through a small angular distance about pin 22towards two spring contacts I9a, I922 adapted to cooperate with theblocks 3a and 3?), respectively. If beam I is horizontal, saiddeflection will not bring about the closure of either contact. However,if the pointer is out of neutral position, either block So will engagecontact Ida, or block 3b will engage contact 1919, so as to switch inthe motor 20 and actuate the valve 8 (not shown in these figures) in theone or the other direction, all as described with reference to Fig. 1.

As will be seen from Fig. 2, those faces of blocks 3a, 3b that areadapted to engage contacts Ida, I9?) are biased, in opposite directions,relative to the vertical plane through the axis of beam I, in suchmanner that the period during which either contact [9a or [9b remainsdepressed by the bell crank i5 is proportional to the deflection of saidbeam. This has the advantage that relatively considerable deviations ofthe density in vat I8 (Fig. 1) from the proper value will be corrected aquickly as relatively small deviations, without, however, giving rise tooscillation of the actual value about the proper one.

Turning to Fig. 3, this illustrates an embodiment similar to thatdescribed with reference to Fig. l but wherein the motor for actuatingthe valve (8 in Fig. 1) is substituted by a mechanical drive. Thisrenders the device especially suitable for use in installations such ascoal washing plants, where rough conditions prevail.

As shown, the ends of the long arms of bell cranks Him, [511 here areconnected to their springs Hoand Ill), respectively, through chains orother flexible members, sheaves around which said members are passed,and arms 28a and 287), respectively, secured to said sheaves. Thefeelers Illa and [8b cooperate with the block 3, which is ofsubstantially the same configuration as block 3 illustrated in Fig. 1,it being understood, however, that the depth of each of the recessestherein increases from the non-recessed central portion towards the topand the bottom face, respectively, of the block, for reasons explainedwith reference to the biased blocks 3a, 311 shown in Figs. 2 and 2a.

The long arm of bellcrank [5a is further connected to one end of a belt23w passed, in clockwise direction, around a wooden sheave 21 adapted toactuate the valve (8 in Fig. 1). The other end of belt 23a is connectedto a frame 24 w urged by a spring 25w into engagement with an abutment28a. In a similar manner, the lon arm of bell crank I52) is associatedwith the sheave 2'! through a belt 23?) passed around it incounterclockwise direction and secured to a frame 24b adapted, under theinfluence of a spring 25b, to engage an abutment 26b.

The lengths of belts 23a, 231) are such that they are slack as long asthe rollers Mia, Mb engage the high portion of cam l3. If, however, thelow portion of the cam reaches the said rollers, and assuming the block3 to have moved in downward direction out of neutral position, crank 55bwill be swung, under the influence of its spring I'lb, through anangular distance sufficient to pull the belt 231) tight around sheave 21and rotate the latter through a small angular distance in clockwisedirection, whereby the valve (8) is actuated so as to increase theamount of light liquid flowing to vat l0, spring 25?) preventing thebelt from slipping. The other bell crank, [5a, is arrested by thenon-recessed portion of block 3 and thus cannot tighten its belt 23a,which, thereby, remains idle.

Attention is drawn to the fact that each of the springs Il a, Hb shouldbe strong enough to adjust the valve (8) to be actuated by sheave 21. Asshown, said springs engage arms 23m and 2822', respectively, each ofwhich, when assuming idle position (see arms 25a.) is nearly in parallelrelation with the axis of the spring associated therewith, but at theend of the working stroke encloses an angle of about 90 with said axis.This. has the advantage that, as long as said arms are inoperative,their springs offer only a minimum of resistance to rotation of cam l3,but are fully effective the moment wherein sheave 2'! is to be rotatedto adjust the valve (8).

Although the embodiment illustrated in Fig. 3 is very suitable forvarious purposes, it has some inconvenience owing to the fact that themoment wherein rollers M a, Mb disengage the high portion of cam IS, thefeelers I811, lab are suddenly arrested by block 3 so that they forciblystrike the block 3. If, now, springs I'm, llb

have to be very strong, the noise caused by these blows could beannoying and even result in rapid wear and tear of the impacting parts.

Figs. 4 and 4a illustrate mechanism which, although somewhat morecomplicated, is devoid of the inconveniences just stated. Also inaccordance with these figures, sheave 2? serves to actuate valve (8).Secured to the end of lever arm lSa (Fig. 4) is one end of belt 23a, theother end of which is secured to the lever arm 24c. Arm l5a is furtherconnected, through a chain 35a, to one arm of a lever 30, which isrotatably mounted on a fixed pivot 33, and the diametrically opposed arm3| of said lever is connected, through chain 34a, to lever arm 24a. Thethird arm 32 of said lever is engaged by a strong coiled spring l1.

Lever arm a is keyed to pivot pin l6 mounted for rotation in the frame(not shown) and is provided with a roller Ida, for engagement with theperiphery of cam 13. The lever arm 24a is loosely mounted on pivot 16and connected, through a spring c, with a lever arm 26a also freelyrotatable about pin l6. Secured to lever arm 26a is the feeler 181w,which is arranged for cooperation with block 3 suspended from one arm ofthe weighing beam from the other arm of which is suspended the body 2.

As long as roller [4a engages the high portion of cam l3, belt 23a isslack and lever arm 26: engages, through a nose 29a, lever arm 24a towhich it is connected by spring 25a. The moment wherein roller Mareaches the "low portion of cam i3, and assuming the density of theliquid in the vat ([0) to have the proper (or a lower) value, spring I!pulls lever arm Ida and, thereby, the left hand side part of belt 23aupwards, but simultaneously it allows lever arm 24a to swing downwardand to lower the right hand part of belt 2311 by the same amount, sothat this belt remains slack. The lever arm 26m and the feeler I804simply follow the downward swinging movement of lever arm 24a, since,under the conditions stated, block 3 assumes a position wherein itsrecessed lower portion faces feeler Illa, so that the swinging movementof the latter is not interfered with.

If, however, the actual value of the density of the liquid in the vat(l9) exceeds the proper value, so that block 3 assumes a position on alower level, feeler law will, during its aforesaid swinging movement, bearrested by the projection or non-recessed upper portion of block 3,which itself is thereby urged against the abutment 5, owing wheretolever arm 26a is also arrested and, through spring 25a, brakes lever arm24a, the consequence being that chain 34a will get slack and belt 23a ispulled tight around sheave 2? under the upward pull of lever arm 30 byspring 11 in combination with the upward pull of lever arm 24a by spring251a. This causes the sheave 27 to be rotated through a small angulardistance, in clockwise direction, under the influence of spring I7,since, as it is pertinent here to state, spring I! is stronger thanspring 25c.

When roller Ma is thereupon urged downward by the high portion of cami3, lever arm We is swung in counterclockwise direction so as to tensionspring [1, lever arm 24a is swung upwards under the pull of chain 34aand lever arm 26a together with the feeler l8a will follow this upwardsswinging movement owing to the engagement of arm 24a, with nose 29a.

When the density of the liquid in the vat I!) is subnormal, the sheave2'! is rotated counterclujockwise by the mechanism shown in Fig. 4a, itbeing understood that the parts i, 2, 3, 5, IE, IT, 30, 3|, 32, 33 arecommon to this mechanism and the one just described with reference toFig. 4, and that the parts marked by reference numerals indexed a inFig. 4, are duplicated in the mechanism shown in Fig. 4a, wherein theirreferences are indexed 1).

Passed around sheave 27 is a second belt 231), whose ends are connectedto lever arms 15b and 2412, respectively. As shown, the positions ofthese arms correspond to those of arms 24a and I5a, respectively, andfeeler [8b cooperates with that part of block 3 whose upper portion isrecessed. Since lever arm 15b is keyed to pivot pin IE and,consequently, is rigidly secured to lever arm l5a (Fig. 4), it is clearthat movement imparted by cam I3 (Fig. 4) to lever arm [5a will betransmitted to lever arm 15b.

In view of the explanations given hereinbefore it is believed that theoperation of the mechanism shown in Fig. la does not require furtherdescription.

Attention is drawn to the fact that, with an arrangement as illustratedin Figs. 4 and 4a, the feelers (I8c, I8b) are caused to engage block 3only under the influence of the weight of lever arms 24 and 26. Bysuitably balancing said weight, the force of the impact can still bereduced. As a matter of course, the pressure exerted by the feelers 0nthe block once they have engaged the same, is thereupon increased by thetension of spring 25, but this pressure is static and, moreover,considerably lower than the one brought about by the springs I'Ia, Ilbin the arrangement described with reference to Fig. 3.

Another advantage of the device shown in Figs. 4, 4a is that the motorfor driving cam 13 has to tension only one spring I! of the samestrength as each of the two springs He, no shown in Fig. 3.

In the device in accordance with Figs. 4, 4a,, the power required forrotating sheave 21 is furnished by spring H, which is periodicallyloaded by the motor for driving cam 13. Said power could, however, alsobe furnished by the motor directly, for instance so that cam I3 directlyengages lever arm 32 and lever arms 15a, 151) are loaded by a spring,which, then, could be essentially weaker than each spring I! in thedevice shown in Fig. 3. This is an advantage when rotation of sheave 21requires a considerable amount of energy.

My invention thus provides simple and reliable means for controlling thedensity of liquid media, although it is also suitable, inter alia, forchecking the weight of packages, dosed solids, etc. As stated before, itis primarily intended for use in coil preparation and, generally spoken,in ore dressing plants, for instance, for controlling a uniform supplyboth of liquid and of solid material to flotation machines, forcontrolling the solid to liquid ratio of pulp in thickeners, forcontrolling the density of coarse ore pulp returned from a classifier toa ball mill whose output is passed through said classifier, forsubstituting the usual automatic controlling devices of jigs wherein thejig-stroke is adjusted in accordance with the thickness of the layer ofsinks, etc.

What I claim is:

1. A system for producing a suspension having a predetermined density bymixing a suspension of variable density with a density adjusting liquid,said system comprising in combination a supply conduit for suspension ofvariable density, a supply conduit for the density adjusting liquid, areservoir adapted to receive the liquids supplied by both said conduitsand provided with a discharge conduit, control valve means in the supplyconduit for the density adjusting liquid, actuating means operable toincrease and to decrease the passage of said control valve means, aweighing beam, means for swingably supporting said beam, means forloading one arm of said beam responsive to the density of the mixture insaid reservoir, means for balancing said beam so that the latter ismaintained in a balanced position when the density of the mixture insaid reservoir is at a predetermined value, two check members ofiset andfixed relative to one another and connected to said weighing beam so asto follow movement of said beam from said balanced position, two feelermeans each adapted to cooperate with a related one of said checkmembers, means for periodically causing movement of said check membersand said feelers relative to one another, and means efiective during theperiodic relative movement of said feelers and check-members foroperating said actuating means in response to the cooperation of saidfeeler means and said check members when said check members aredisplaced by movement of said beam from its balanced position.

2. A system in accordance with claim 1, wherein said check members areprofiled as to hold said actuating means in operative position during aperiod proportional to the deflection of the weighing beam.

3. A system in accordance with claim 2, wherein the feeler means areloaded by spring means tending to urge them into engagement with theprofiled check members.

4. A system in accordance with claim 1, wherein the feeler means areoperatively coupled with the actuating means through mechanical means.

5. A system in accordance with claim 1, wherein the feeler means arecoupled through spring means with periodically operated mechanical meansfor imparting movement to the actuating means.

6. A system in accordance with claim 4, wherein said mechanical meanscomprise a sheave for imparting movement to the actuating means, and abelt passed around said sheave, said belt being operative only when saidcheck members interfere with the periodic movement of the feeler means.

7. A system according to claim 1 in which said check members havesurfaces normally spaced from said feeler means, said surfaces beingnon-parallel to the general plane of deflection movement of said membersand in which said feeler means engage said surfaces for a period of timeproportional to amount of deflection of said check members resultingfrom the deflection of said beam.

8. A system according to claim 1, wherein said means for operating theactuating means includes a sheave for imparting movement to saidactuating means, at least one belt passed around said sheave, said beltbeing connected to and movable by said periodical movement causingmeans, and means connected to said feelers for tighten- ,ing andloosening said belt on said sheave according to the position of saidcheck members.

9. A system according to claim 1, wherein said means for operating theactuating means includes switch means for causing energization of saidactuating means, said switch means being actuated by said feeler means.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,178,193 Trimbey Apr. 4, 1916 1,210,180 Logan 1 Dec. 26, 19161,664,840 Wermine Apr. 3, 1928 1,892,839 Howard a- Jan. 3, 19331,966,638 Morgan July 1'7, 1934 2,332,953 Tromp Oct. 26, 1943 2,490,634Keene Dec. 6, 1949

